eLearning 101: Simple video editing in Camtasia
This video is focusing on fast editing methods of videos for teaching and learning. This video shows how to do it in Camtasia, it costs money but has a 1-month free trial and a reasonable education rebate.
Other good alternatives:
OpenShot (Win, Mac, Linux) free
iMovie (Mac) free
They all use the same principles shown in the video.